interface Shape {
    double area(double givenValue);
}
class Square implements Shape{
    public double area(double sideLength) {
        return sideLength*sideLength;
    }
}
class Circle implements Shape{
    public double area(double r) {
        return Math.PI*r*r;
    }
}
public class text{
    public static void main(String[] args) {
        Shape square = new Square();
        Shape circle = new Circle();
        System.out.println(square.area(2));
        System.out.println(circle.area(5));
    }
}